This invention relates to sewing machines and more particularly to an improved needle guard for sewing machines.
The present invention is a further development of the machine forming the subject matter of U.S. Pat. No. 4,077,342 granted Mar. 7, 1978 to P. E. Steckenrider. In such machines a rotary loop taker is disposed beneath a flat work supporting plate which is provided with an aperture to receive a substantially vertically disposed needle adapted for reciprocation through such aperture for the purpose of cooperating with the loop taker in the formation of stitches. In descending, the needle passes in close proximity to the path of the beak of the rotating loop taker and on its upstroke the needle throws out a thread loop which is entered by the beak after which the beak carries the needle thread loop about the lower stitch forming mechanism. In the event that the needle is bent or deflected by heavy weight materials, a cross seam or any irregularity in the material being sewn, it may, during its descent, strike the rotary loop taker with the result that the hook may be scored or otherwise damaged, or the needle may be broken.
In addition, the taper of many types of needles used in sewing machines has different configurations depending upon the material being stitched. The presence of the different tapers and different diameter needles makes it very desirable to provide a needle guard having the capabilities whereby it can be accurately adjusted to function with the particular needle chosen for the material to be stitched.
So as to overcome the above mentioned problems it has been heretofore proposed to provide a needle guard which is fastened for rotation and operable with the rotary hook. It is known to provide the hook with a deflecting surface so as to assure positioning of the needle relative the loop seizing beak. However, by positioning a needle guard on only one side of the needle it may not be possible to prevent skewing of the needle in a direction away from the loop seizing beak. When the needle skews away from the loop seizing beak there remains the possibility of needle breakage and hook damage and in addition there is a greater chance of skipped stitches resulting in poor seams and inacceptable garments. Further, some of the heretofore known needle guards are actuated in timed relationship with needle reciprocation whereby requiring additional mechanisms and thus added costs to the price of the machine.
As particularly applicable to the present invention, the problem of providing a needle guard for a machine of the type described in the above identified patent is further enhanced by the thread cutting mechanism which is employed thereon. The problem is enhanced because the path of movement of the thread cutting mechanism requires that at least one of the cutting blades traverse the plane defined by the needle's path. In this regard, it is necessary not only for the present invention to be able to prevent needle skewing but also requires that the needle guard be removed from the area proximate the needle's path upon completion of the sewing operation so as to allow subsequent trimming operations to be executed. In accordance with the present invention needle skewing is substantially eliminated and a device is provided which can be retracted from the sewing area so as not to interfere with subsequent trimming operations. Further, the present invention is relatively easily adjustable in a manner which allows adjustment of the needle guard relative the path of the needle as will be apparent hereinafter. An additional advantage of the present invention is that, because of its presence in the proximity of the needle during sewing, it acts to prevent formation of an appreciable thread loop opposite the looptaker so as to minimize skipped stitches.